Measurement instruments commonly sample an analog input signal and convert it into a digital representation. Many of these instruments rely on delta-sigma analog-to-digital converters (ADCs) to perform the conversions. The delta-sigma ADCs may, in turn, include internal ADCs as components. If an internal ADC does not function in a linear manner, however, the accuracy of the total analog-to-digital conversion will suffer. Therefore, what is needed is a method and apparatus for detecting and correcting non-linearity of an internal ADC within a delta-sigma ADC.